import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

/**
 * @Author Fizz Pu
 * @Date 2020/12/8 下午5:24
 * @Version 1.0
 * 失之毫厘，缪之千里！
 */
public class OjB {
    public static void main(String[] args) {
        Map<String, Double> score = new HashMap<>(8);
        score.put("A",4.0);
        score.put("B",3.0);
        score.put("C",2.0);
        score.put("D",1.0);
        score.put("F",0.0);
        Scanner scanner = new Scanner(System.in);

        while (scanner.hasNextLine()){
            String[] data = scanner.nextLine().strip().split(" ");
            double sums = 0;
            int flag = 0;
            for(String each : data){
                if(!score.containsKey(each)){
                    flag = 1;
                    break;
                }
                sums += score.get(each);
            }
            if(flag == 1) {
                System.out.println("Unknown");
            } else {
                System.out.printf("%.2f\n", sums / data.length);
            }
        }
    }

}
